SECRET cameras are being placed on beaches and in the water to catch jetski hoons.

Authorities are also using helmet cams to gather evidence of jetskiers speeding, drag racing and riding too close to each other.

The Herald Sun joined Transport Safety Victoria and saw beachgoers risking their lives and jetski riders hooning on the water.

Others had jetskis and boats in banned areas while teens were observed jumping from a tower, where only a day earlier My Kitchen Rules contestant Harry Curtis fractured two vertebrae in his neck.

The crackdown on speeding jetskis and dangerous behaviour is alarming police.

Transport Safety Victoria marine safety officer Marty O'Connell said the most powerful jetskis could hit speeds of up to 115km/h and their riders had limited reaction time.

"They ride really close to each other and if they hit each other at those kinds of speeds they will cause incredible damage and serious injury," Mr O'Connell said.

"There are also swimmers in the water and you can only see the top of their heads - and by that stage it's too late."

Mr O'Connell said crews would be on the water and ready to pounce when radioed by other officers that observe the riders.

The footage would be used for court purposes if challenged. TSV data shows there have been four boating collisions since December with one resulting in the death of 12-year-old Courtney Keast in Lake Eppalock after her family's boat collided with another.

Two other men were injured in the same crash, and Victoria Police is still investigating.